Presses

ABSTRACT

A press particularly intended for use in the pressing of blocks or sheets of a synthetic plastics material has a crank drive mechanism and a hydraulic drive mechanism and the two drive mechanisms are so controlled as to obtain rapid opening and closing of the press while maintaining straight-line movement of the ram of the press.

United States Patent Sharman 1 1 Aug. 1, 1972 s41 PRESSES [56] References Cited [72] Inventor: John Charles Sharman, Walsall, En- UNIT STATES PATENTS gland 2,962,993 12/1960 Johansen ..74/44 x [73] Assignee: G.K.N. Engineering Limited, 3,129,799 4/1964 Dean et a1 ..100/53 X Redditch, England 3,348,406 10/1967 l-lolberson ..100/257 X [22] Filed: 1970 Primary Examiner-Robert L. Spicer, Jr. I [211 App]. 2 3 Attorney-Merria'm, Marshall, Shapiro & Klose [57] ABSTRACT [52] 2 3 1 3 5 A press particularly intended for use in the pressing of blocks or sheets of a synthetic plastics material has a ll!!- CI. U28 crank drive mechanism and a hydraulic drive [58] Flew Search "18/16 16 19 mechanism and the two drive mechanisms are so controlled as to obtain rapid opening and closing of the 7 2 Claims, 3 Drawing Fig ures PATENTEDAUE 1 I972 SHEEI 2 (IF 3 PRESSES 1 Field of the Invention This invention relates to presses of the kind which include a main frame having guide means for guiding a sub-frame for movement relative to the main frame such that a reference plane on the sub-frame parallel to a reference plane on the main frame is maintained in this parallel condition with a first drive means for moving the sub-frame relative to the main frame and a second drive means for effecting relative axial movement between a pair of platens provided one on the main frame and the other on the sub-frame.

2. Description of the Prior Art Presses of the above kind are known for use in the forming of small plastics objects in which the maintenance of parallel conditions between the sub-frame and the main frame is not critical and in which the size of the objects is not such as to require the distance of opening movement of the sub-frame to be substantial thereby not requiring means for effecting rapid movement of the sub-frame relative to the main frame.

Such a press is disclosed in German Pat. specification No. 1,21 1,376 and the press of that specification is intended particularly for impressing sound grooves in records.

It is an object of the present invention to provide a press, particularly for use in the formation of large plastics articles such as parts of motor vehicle bodies, which includes improved means for maintaining parallel conditions between the sub-frame and the main frame.

SUMMARY OF THE INVENTION The press of the present invention comprises, a base; a first platen carried by the base; a head; fixed supporting and guiding members extending between and secured to the base and the head; a sub-frame between the base and the head, guidingly engaged with said members and movable vertically relative to the base; a second platen carried by the sub-frame between the sub-frame and the first platen, guidingly engaged with frame for moving the second platen relative to the subframe.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view of the press, ,FIG. 2 is a perspective view, from above, of the press shown in FIG. 1 but with the relative dispositions of the driving motor and its associated parts slightly changed and FIG. 3 is a detail sectional view of part of the press.

DESCRIPTION OF THE PREFERRED EMBODIMENT The press shown in the drawings can be used in operating on blocks or sheets or other preformed shapes of a synthetic plastics material reinforced by, for example, glass or asbestos fibers, the plastics material comprising, for example, a major proportion of a thermosetting resin and a minor proportion of a. thermoplastic resin, the ingredients of the plastics material being such that, on curing or polymerizing, there is no shrinkage or very little shrinkage.

The press can also be used for operating on blocks or I sheets of thermoplastic material which have been preformed and in some cases preheated as required, prior to being placed in the press, the tools of which can be cooled or maintained at a predetermined temperature, so that, on full closure of the press, a simple or complex moulding is formed. The thermoplastic material may contain a reinforcement.

The press can also be used for operating on thermoplastic or therrnosetting materials, with or without a reinforcement, which are injected into the press dies either while the press is open, or is closing, or is fully closed. The press can also be used for operating on blocks or sheets or preformed shapes of metals or alloys, such as aluminum alloys, which may contain a reinforcement such as carbon fibers.

The press includes a main frame 10 having a base 11 and a pair of end members 12 and 13. The base 11 supports a fixed platen 14 which-is formed with two or more T-section elongated grooves 15 for mounting a tool thereon. Four vertical guides or guiding and supporting members 16 of circular cross-section extend upwardly from the base '11 and the guides are located two at each side of the fixed platen 14 and at their A upper ends the guides 16 carry a rectangular box-section framework or head 17 which serves to hold the guides 16 against movement relative to each other in their required vertical disposition. The guides 16 serve to guide a sub-frame 18 for vertical movement relative to the main frame 10 and first drive means is'provided for effecting the vertical movement of the sub-frame 18. The sub-frame 18 is shown in FIG. 1 in its fully lowered position whereas it is shown in FIG. 2 in a position approaching its fully up position.

As shown the first drive means includes an electric motor 19 which, through a pulley and clutch mechanism, drives a main drive shaft 20 extending beneath the base 11 from side-to-side thereof.

The press shown in FIG. 2 is intended to be mounted on the floor of a machine shop with the main drive shaft 20 above the level of the floor but with the motor 19 located in a small well in the floor. The press shown in FIG. 1 is intended, however, to be positioned with the main drive shaft 20 positioned below the level of the floor in' the shop, the well construction and the disposition of the motor 19 relative to the shaft 20 being clearly shown in FIG. 1.

In the construction shown in FIG. 2, the main drive shaft 20 carries a pair of gears 21 which mesh with gear plates 22 mounted on a crankshaft 23 also extending from side-to-sicle of the press and contained within the base 1 l, the crankshaft 23 being supported in bearings 24 carried by the side members 12 and 13 of the frame.

The main drive shaft 20 of the press shown in FIG. 1 also carries a pair of gear wheels which mesh with gear plates 22 mounted on a crankshaft 23.

Connecting rods 25 are connected eccentrically to the plates 22 and the upper ends of the connecting rods 25 are attached to clevises 26 on the sub-frame 18.

When the motor 19 is operating, it transmits drive to the crankshaft 23 which effects reciprocal movement of the sub-frame 18 relative to the main frame 10. The two connecting rods 25 are aligned with each other and a stress loop system is thus set up, the system comprising the crankshaft 23, the two connecting rods 25 and the sub-frame 18. During movement of the sub-frame 18 relative to the main frame 10, the guides 16 which maintain the sub-frame in a horizontal condition are thus not subjected to any appreciable bending stresses since the guides 16 serve merely to assist in the maintenance of the sub-frame 18 in its horizontal condition, this arrangement ensuring that a reference plane on the sub-frame 18 originally parallel to a reference plane on the main frame will be maintained in this parallel condition.

At the lower end of its stoke the sub-frame 18 can be maintained in its lower or bottom dead center position by application of a brake 27 and by means of a locking mechanism which includes a hydraulically operated plunger 28 arranged to enter a recess 29 formed in one of the gear plates 22. The press includes a main pump (not shown) which operates the brake 27 and provides hydraulic fluid to the cylinder containing the plunger 28, a sensing element (not shown) being provided associated with the plunger 28 to sense when the recess 29 is in the appropriate position and thus to operate the brake 27 and to move the plunger 28 outwardly of its cylinder.

A pair of balance cylinders 30 are carried by the boxsection framework 17 attached to the upper ends of the guides 16, the pistons contained within the cylinders 30 being connected to the sub-frame 18, and, as can be seen from FIG. 2, the balance cylinders 30 are positioned one at each side of the main vertical axis of the press and the cylinders 30 assist in effecting balancing of the sub-frame 18 during its reciprocal movement relative to the main frame 10.

The sub-frame 18 carries a number of piston and cylinder mechanisms, the number depending on the rating of the press, the cylinder or cylinders 31 being fixed relative to the sub-frame l8 and the or each piston 32 is connected to a platen 33 which being of rectangular form in plan view and includes bearing collars 34 which receive the guides 16 whereby said platen 33 is guided by said guides 16 and is movable relative to the sub-frame 18' on operation of the piston and cylinder arrangement 31, 32 carried by the sub-frame 18. As shown in FIG. 3, the platten 33 is provided with a plurality of elongated slots for the mounting of a tool 35. The platen 33 is connected by a pair of vertical rods 36 to each of a pair of frame members 37, each frame member 37 being connected by a pair of pull-back piston and cylinder mechanisms to the sub-frame 18. The arrangement is that the platen 33 can be moved downwardly relative to the subframe 18 on energization of the piston and cylinder arrangement 31, 32 and pulled back or moved upwardly by means of the pull- I back cylinders 38.

The top and bottom dead center positions of the subframe 18 relative to the main frame 10 can be adjusted by means of a ram adjustment gear which includes a motor 39 which drives a shaft 40 which, through a gear mechanism 41, can move the clevis 26 relative to the sub-frame 18.-

In operation, the sub-frame 18 is moved downwardly relative to the main frame 10 into its lowered bottom dead center or closed position and it can then be locked in this positionv by means of the plunger 28. Hydraulic fluid is then supplied under pressure to the cylinders 31 carried by the sub-frame 18 to move the movable platen 33 downwardly relative to the subframe 18, such downward movement being effected at an adjustable and controllable rate. The movable platen is then maintained in its closed position for a predetermined time, during which polymerization or solidification of the synthetic plastics material takes place according to its formulation and the material is caused to maintain the shape into which it has been pressed. Hydraulic fluid is then supplied under pressure to the pull-back cylinders 38 mounted on the sub-frame 18 to retract the movable platen 33. At this time or during retraction of the platen 33, the plunger 28 is retracted and the sub-frame 18 is then moved upwardly into its upper, top dead center or open position in which it can again be locked by operation of the plunger 28 and the formed workpiece is then removed.

Curing or polymerization or solidification of the synthetic plastics material is effected by means of heat or controlled cooling according to whether the material being pressed is thermosetting or thermoplastic and the platens or tools carried thereby can therefore be hollow whereby steam or water can be used to effect heating or cooling. Other heating or cooling means can, alter natively, be provided.

An important advantage of the press shown in the drawing is that, as the drive to the sub-frame 18 is independent of the drive to the movable platen 33, rapid movement of the sub-frame can be effected by the crank drive mechanism while the movable platen 33 is movable under the control of a hydraulic piston and cylinder mechanism or mechanisms and can therefore be moved at an adjustable and controllable rate and can be maintained at any position for any desired period of time.

The drive to the movable platen 33 can be rendered operative either after the sub-frame 18 has been locked in its bottom dead-center position or during movement of the sub-frame 18 into its bottom dead center position and upward movement of the sub-frame 18 relative to the main frame 10 can be effected simultaneously with upward movement of the movable platen 33 relative to the sub-frame 18.

In order to simplify the design of the press when producing a range of presses of different ratings, the sub-frame can be designed so as to accommodate a plurality of hydraulic cylinders each having pistons connectable to the movable platen so that, to produce a range of presses having, say four different ratings, the sub-frame of one press will contain one hydraulic cylinder, the sub-frame of another press will contain two hydraulic cylinders, the sub-frame of a further press will contain three hydraulic cylinders and the subframe of the last press will contain four hydraulic cylinders.

The four vertical guides 16 are arranged so as to permit the work to be operated on to be introduced from one end of the press and discharged from the other end of the press so as to obtain a continuous flow in the passage of the articles being pressed and it is to be noticed that the guides 16 will only be subject to stresses acting transversely of their axes when the subframe 18 is in its lowered or bottom dead center position and the movable platen 33 is in its lowered position, i.e., only during the shaping of the workpiece and the moments of the bending stresses transmitted to the guides 16 will therefore be a minimum. Accurate maintenance of the sub-frame l8 and of the movable platen 33 in a horizontal condition will thus be attained.

The press can be used for the production, not only of plastics articles or metal articles, but also for the production of plastics articles formed from mixed thermoplastic and thermosetting materials having low shrinkage characteristics with the incorporation of metal or other inserts. The inserts can be wholly encapsulated within the plastics material or may project therefrom and can provide, for example, fixing lugs or screw-threaded sockets.

During the downward movement of the sub-frame 18 under the action and control of the associated crankdrive system, the rate of downward movement of the sub-frame is considerably reduced as the sub-frame 18 approaches its lower or bottom dead-center position. During such downward movement of the sub-frame 18 hydraulic fluid is supplied to the piston and cylinder mechanism 31, 32 so as to move the platen 33 downwardly relative to the sub-frame 18.

The motion of the platen 33 during closing of the press thus includes a first component derived from the motion imparted by the crank-drive system and a second component derived from the motion of the hydraulic piston and cylinder mechanisms.

The crank-drive mechanism provides for rapid opening and closing of the press and, as it may be required to move the upper platen 33 a distance of say 4 feet or more above the lower platen, it is important that, for rapid production, the platten.33 should be movable rapidly.

For accurate deformation of the synthetic plastics material it is important that, during movement of the platen 33 to effect deformation of the synthetic plastics material, the platen moves in an accurate and controlled manner with a predetermined pressure applied to effect the deformation of the plastics material.

It is essential that, when forming, for example, a hood of a motor vehicle or a body of a motor vehicle, the finished pressing should be of controlled thickness and of controlled surface finish and this is obtained by ensuring that, throughout its movement, the platen 33 is maintained in a condition parallel to the fixed platen on the bed of the press.

I claim:

1. A power press comprising a base; a first platen carried by and fixed to the base; a head; fixed supporting and guiding members extending between and secured to the base and the head and being located outside said first platen; a sub-frame between the base and the head, guidingly engaged with said members and movable vertically relative to the base; a second platen carried by the sub-frame between the sub-frame and the first sazztt esaai tasrt ia trsturtrse wii guided by said members to remain parallel to the first platen; first drive means in the form of a horizontal crank-shaft mounted below the first platen and connecting rods between the crankshaft and the sub-frame for moving the latter, the connecting rods being connected to the sub-frame adjacent the ends thereof and being located outside the supporting members; and second drive means carried by the sub-frame for moving the second platen relative to the sub-frame.

2. A power press according to claim 1 wherein the supporting and guiding members are in the form of columns which are embraced by collars on the subframe and the second platen. 

1. A power press comprising a base; a first platen carried by and fixed to the base; a head; fixed supporting and guiding members extending between and secured to the base and the head and being located outside said first platen; a sub-frame between the base and the head, guidingly engaged with said members and movable vertically relative to the base; a second platen carried by the sub-frame between the sub-frame and the first platen, guidingly engaged with said members and movable vertically relative to the sub-frame while guided by said members to remain parallel to the first platen; first drive means in the form of a horizontal crank-shaft mounted below the first platen and connecting rods between the crankshaft and the sub-frame for moving the latter, the connecting rods being connected to the sub-frame adjacent the ends thereof and being located outside the supporting members; and second drive means carried by the subframe for moving the second platen relative to the sub-frame.
 2. A power press according to claim 1 wherein the supporting and guiding members are in the form of columns which are embraced by collars on the sub-frame and the second platen. 